The increasing world population and the demand to improve quality of life for a large percentage of human beings are the driving forces for the development of sustainable clean energies. Fuel cells, i.e. electrochemical devices that directly and efficiently convert chemical energy into electrical energy, have received growing interest in recent decades since they are the most promising, efficient, and environmentally benign energy-conversion devices. Among all types of fuel cells, solid-oxide fuel cells (SOFCs) possess the advantages of flexible fuels, high efficiencies, cost-effective electrodes, and rapid electrode reactions. However, the necessity for high operating temperatures has resulted in high costs and materials compatibility challenges.
The basic structure of a fuel cell consists of a fully dense electrolyte ceramic oxide sandwiched between a porous anode and a porous cathode. For the realization of this single cell configuration, multi-step preparation methods are usually employed (as illustrated in FIG. 1), which inevitably involve the synthesis of high-quality componential powders (electrolyte, anode, and cathode) from expensive precursors (e.g. nitrates) by complicated wet-chemistry routes and multi-time high temperature calcination and sintering (e.g. the dense electrolyte needs sintering temperature >1600° C.). As a result, the produced materials always need long processing time and high processing cost, which limits their practical application.
A key obstacle to reduced-temperature operation of PCFCs is the low activity of poorly-structured cathode attached to electrolyte membrane by high-temperature annealing (>1000° C.). Thus, a need exists for PCFCs that are easy and cost-effective to fabricate, while maintaining their high-performance. A need also exists for an intermediate-temperature (between about 300-600° C.) single cells with well-nanostructured cathodes involving low electrolyte densification temperatures (<1400° C.) and low cathode attaching temperature (<900° C.).